Light emitting circuit and lighting device

ABSTRACT

A light emitting circuit includes: a first circuit H 1  in which is provided a main light source  5, 6;  and a second circuit H 2  connected in parallel with the first circuit H 1  and in which is provided an auxiliary light source  1, 2  and  3;  wherein a drain (D) and a source (S) of an field effect transistor  4  are connected in the second circuit H 2,  and a gate (G) of the field effect transistor  4  is connected to the first circuit H 1.

FIELD OF THE INVENTION

[0001] The present invention relates to a light emitting circuit and alighting device for a vehicle, which are particularly used for a sideturn light provided at an outer mirror of a vehicle.

BACKGROUND ART

[0002] As a high mounted stop lamp, etc. provided at the rear of thevehicle, an LED or the like has been utilized because it requires lesselectric power consumption and emits light at high luminance. As shownin FIG. 6, this high mounted stop lamp comprises a circuit formed by aplurality of parallelly connected LED groups L1˜L6, each including thesame number of LEDs (four in FIG. 6) connected in series. With thisarrangement, even if one LED (any one of LEDs D1˜D24) malfunctions, therest of the LED groups L1˜L6 satisfies the demand luminous energyregulated by law.

[0003] There is a lighting device with a circuit arrangement similar tothis high mounted stop lamp, wherein a main light source that emitslight with greater luminous energy in order to satisfy the regulation bylaw and an auxiliary light source that is used for accessories to dressup the vehicular design are connected parallelly.

[0004] This kind of lighting device has been adapted to side turn lightsfor indicating a change of the direction of the vehicle.

[0005] Generally, the side turn lights are provided at side surfaces ofthe vehicle, and in this instance, the lighting device having theaforementioned circuit arrangement is not required. However, in recentyears, the side turn lights have been provided at the outer mirrorsinstead of being provided at both side surfaces of the vehicle body forthe purpose of dressing up the vehicle, and therefore the lightingdevice has been applied for outer mirrors. In other words, in order tobe visible from the sides and the rear of the vehicle, the main lightsource emitting a sufficient luminous energy that satisfies theregulation is arranged at both edges of the outer mirrors, remotely fromand outside of the vehicle compartment, and the auxiliary light sourcefor accessories is arranged at a front of each outer mirror in aposition parallel to the main light source.

[0006] According to the arrangement of the circuit where the main lightsource and the auxiliary light source are merely connected in parallel,even if one of the light sources malfunctions, the emission of light iscontinued by the other light source. Therefore, it is difficult for thedriver to recognize the malfunction of the side turn light. Especially,a problem arises when the main light source is run down, because theauxiliary light source continuously emits light with the luminous energyunsatisfying the regulation and the driver may misunderstand that theside turn lights function normally.

[0007] The technological problem to be solved by the present inventionshould be focused in this point, and the object of the invention is toprovide a light emitting circuit and a lighting device for a vehicle,which are particularly used for a side turn light provided at an outermirror of the vehicle, and which stops the emission of light of theauxiliary light source when the main light source is run down so thatthe run down of the main light source is reliably informed to thedriver.

SUMMARY OF THE INVENTION

[0008] In order to achieve the above objective, a light emitting circuitaccording to the invention comprises: a first circuit in which isprovided a main light source; and a second circuit connected in parallelwith the first circuit and in which is provided an auxiliary lightsource; wherein a drain and a source of an field effect transistor areconnected in the second circuit, and a gate of the field effecttransistor is connected to the first circuit.

[0009] According to this light emitting circuit, both the main lightsource and the auxiliary light source emit light in the normal state,however, since one end of the first circuit is connected to the gate ofthe field effect transistor, the gate voltage becomes zero when the mainlight source is run down. Therefore, an electric current between thesource and the drain of the field effect transistor is shut down so thatan electric current does not flow into the second circuit, and theauxiliary light source stops the emission of light. As a result, all thelight sources stop the emission of light (lights out state). This makesthe driver reliably recognize the run down of the main light source. Ifthe auxiliary light source is run down, the main light sourcecontinuously emits light.

[0010] Also, in order to achieve the above objective, a lighting devicefor a vehicle, which is provided in an outer mirror of a vehicle,comprises: a main light source arranged at a side of the outer mirror;an auxiliary light source arranged at a front of the outer mirror; and alight emitting circuit having a first circuit in which is provided themain light source, and a second circuit connected in parallel with thefirst circuit and in which is provided the auxiliary light source,wherein a drain and a source of an field effect transistor are connectedin the second circuit, and a gate of the field effect transistor isconnected to the first circuit.

[0011] According to this lighting device for a vehicle, at the side ofthe outer mirror is arranged the main light source emitting a sufficientluminous energy that satisfies the regulation by law, and the auxiliarylight source for accessories is arranged at the front of the outermirror. In this lighting device, the first circuit where the main lightsource is provided is connected to the gate of the field effecttransistor, and if the main light source is run down, the gate voltagebecomes zero, so that an electric current between the source and thedrain of the field effect transistor is shut down and the auxiliarylight source provided in the second circuit stops the emission of light.On the contrary, if the auxiliary light source is run down, the mainlight source continuously emits light. With this construction, if themain light source is run down, both of the main light source and theauxiliary light source provided at the outer mirror stop the emission oflight. This can make the driver immediately recognize the run down ofthe main light source to perform a suitable maintenance.

[0012] Further, a light emitting circuit according to the presentinvention comprises: a first circuit in which is provided a main lightsource; and a second circuit connected in parallel with the firstcircuit and in which is provided an auxiliary light source; wherein anemitter and a collector of a bipolar transistor are connected in thesecond circuit, and a base of the bipolar transistor is connected to thefirst circuit.

[0013] According to this light emitting circuit, like the aforementionedlight emitting circuit, both the main light source and the auxiliarylight source emit light in the normal state, however, since the firstcircuit is connected to the base of the bipolar transistor, the basevoltage becomes zero when the main light source is run down. Therefore,an electric current between the emitter and the collector of the bipolartransistor is shut down so that an electric current does not flow intothe second circuit, and the auxiliary light source stops the emission oflight. As a result, all the light sources stop the emission of light(lights out state). This makes the driver reliably recognize the rundown of the main light source. If the auxiliary light source is rundown, the main light source continuously emits light.

[0014] Further, a lighting device for a vehicle according to the presentinvention, which is provided in an outer mirror of a vehicle comprises:a main light source arranged at a side of the outer mirror; an auxiliarylight source arranged at a front of the outer mirror; and a lightemitting circuit having a first circuit in which is provided the mainlight source, and a second circuit connected in parallel with the firstcircuit and in which is provided the auxiliary light source, wherein anemitter and a collector of a bipolar transistor are connected in thesecond circuit, and a base of the bipolar transistor is connected to thefirst circuit.

[0015] According to this lighting device for a vehicle, at the side ofthe outer mirror is arranged the main light source emitting a sufficientluminous energy that satisfies the regulation by law, and the auxiliarylight source for accessories is arranged at the front of the outermirror. In this lighting device, the first circuit where the main lightsource is provided is connected to the base of the bipolar transistor,and if the main light source is run down, the base voltage becomes zero,so that an electric current between the collector and the emitter of thebipolar transistor is shut down and the auxiliary light source providedin the second circuit stops the emission of light. On the contrary, ifthe auxiliary light source is run down, the main light sourcecontinuously emits light. With this construction, if the main lightsource is run down, both of the main light source and the auxiliarylight source provided at the outer mirror stop the emission of light.This can make the driver immediately recognize the run down of the mainlight source to perform a suitable maintenance.

[0016] Furthermore, in the aforementioned light emitting circuit andlighting device for a vehicle, the main light source emits light at aluminance higher than the auxiliary light source.

[0017] According to these light emitting circuit and lighting device fora vehicle, the light emitting circuit or the lighting device for avehicle is formed from the main light source and the auxiliary lightsource, and the main light source uses a luminous member with higherluminance so that the emission of light only by the main light sourcesatisfies the regulation. Therefore, a cheap luminous member with lowerluminance may be used as the auxiliary light source to decrease theproduction cost. As described above, since a cheap luminous member isused as the auxiliary light source, it is possible to reduce the numberof luminous members unless spoils the design as well as to decrease theproduction cost. Meanwhile, if not decrease the production cost, thenumber of luminous members used for the auxiliary light source can beincreased at the same cost so that the luminescence area is increased toimprove the design. As the luminous member, an LED is preferable.

[0018] Furthermore, in the aforementioned lighting device for a vehicle,the outer mirror is a door mirror.

[0019] According to this lighting device for a vehicle, since thelighting device according to the invention is incorporated in a doormirror, the lighting device can be provided at a position higher thanthe conventional lighting device, leading to improved visibility fromothers at the time of emission.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 is a front elevation of a door mirror incorporating alighting device according to the invention, viewing from the rear of avehicle body.

[0021]FIG. 2 is a side elevation of the door mirror incorporating thelighting device according to the invention.

[0022]FIG. 3 shows the door mirror incorporating the lighting deviceaccording to the invention, viewing diagonally from the front of thevehicle body.

[0023]FIG. 4 is a sectional view taken along the line A-A of FIG. 1.

[0024]FIG. 5 is a circuit diagram of a light emitting circuit used forthe lighting device according to the invention.

[0025]FIG. 6 is a circuit diagram of a high mounted stop lamp.

BEST MODE FOR CARRYING OUT THE INVENTION

[0026] With reference to the drawings when necessary, a preferredembodiment of the present invention will be described.

[0027]FIG. 1 is a front elevation of a door mirror incorporating alighting device according to the invention, viewing from the rear of avehicle body, FIG. 2 is a side elevation of the door mirror, FIG. 3shows the door mirror viewing diagonally from the front of the vehiclebody, FIG. 4 is a sectional view taken along the line A-A of FIG. 1, andFIG. 5 is a circuit diagram of a light emitting circuit used for thelighting device according to the invention.

[0028] A door mirror 11 is used for viewing the rear side, and ismounted near a front end of a door frame of a front door. The doormirror 11 includes a base 12 to be a connecting member to the vehiclebody, a housing 13 retained by the base 12 and supporting a mirror 14,and a driving device 15 (FIG. 4) accommodated in a space formed betweenthe mirror 14 and the housing 13 and changing the reflection angle ofthe mirror 14. The housing 13 has a shape which does not include anyprojections, and rotates backwards of the vehicle body when a certainforce is applied from the front side.

[0029] A lighting device 16 according to the invention (hereinafterreferred to as a side turn light 16) is provided at the housing 13. Theside turn light 16 includes a main light source 16 a arranged at anarcuate end part of the housing 13 which remotes from the vehiclecompartment, and an auxiliary light source 16 b arranged on a surface ofthe housing 13 and extending from the main light source 16 a at acertain length.

[0030] Arrangement of the main light source 16 a and the auxiliary lightsource 16 b is shown by the sectional view of FIG. 4. As the main lightsource 16 a, high-luminance LEDs 5, 6, which emit light with luminancehigher than the auxiliary light source 16 b to be described later and tosatisfy the regulation by law, are arranged along the surface of thehousing 13 at a position visible from the rear and the side of thevehicle and form a first circuit H1 (FIG. 5). As the auxiliary lightsource 16 b, three LEDs 1, 2 and 3 are arranged along the surface of thehousing 13, extending from the main light source 16 a and towards thefront of the vehicle, and form a second circuit H2 (FIG. 5).

[0031] The side turn light 16 turns on and off at a predetermined timeinterval when the vehicle changes the route, so as to inform rear andside vehicles about the change of the route. The luminous energy of theside turn light 16 is determined by law. Since the main light source 16a is arranged at the arcuate end of the housing 13 remotely from thevehicle compartment and is visible from the side and the rear of thevehicle, it substantially functions as the side turn light 16.Therefore, the main light source 16 a alone is required to emit lightwith the luminous energy that satisfies the regulation. On the contrary,since the auxiliary light source 16 b is not visible from the rear ofthe vehicle, as clearly shown by FIG. 1 and the like, and is merely usedfor an accessory to improve the design of the vehicle, the luminousenergy of the auxiliary light source 16 b at the time of emission may besmaller than that of the main light source 16 a.

[0032] Next, with reference to the circuit diagram of FIG. 5, operationof the side turn light 16 according to the invention will be described.

[0033] The light emitting circuit shown in FIG. 5 consists of the firstcircuit H1 and the second circuit H2, which are parallelly branched offat a connecting point J1. The first circuit H1 includes high-luminanceLEDs 5, 6, which are connected in series, and the second circuit H2includes LED 1, LED 2, and LED 3, which are connected in series.

[0034] The cathode of the LED 3 in the second circuit H2 is connected tothe drain (D) of an enhancement-mode field effect transistor (FET) 4through a resistance R1, and the source (S) of the FET 4 is connected toa circuit from the first circuit H1 at a connecting point J3.Accordingly, since the LEDs 1, 2 and 3 of the second circuit H2 areconnected to the source (S) and the drain (D) of the enhancement-modeFET 4, as long as a certain voltage is applied to the gate (G) of theFET 4 to be described later, the LEDs 1˜3 of the second circuit H2 canemit light.

[0035] Meanwhile, the cathode of the high-luminance LED 6 in the firstcircuit H1 is branched off at a connecting point J2, and one end ofwhich is connected to the gate (G) of the FET 4. Therefore, unless thefirst circuit H1 is run down, a certain voltage is applied to the gate(G) of the FET 4. The other end of the cathode that is branched off atthe connecting point J2 is connected to a circuit from the secondcircuit H2 at the connecting point J3 through a resistance R2.

[0036] As high-luminance LEDs 5, 6 used in the first circuit H1, an LEDwhich emits light at higher luminance so as to satisfy the regulation bylaw may be preferably employed. As LEDs 1, 2 and 3 used in the secondcircuit H2, since a particular demand such as required forhigh-luminance LEDs 5, 6 is not necessary, the standard of the LEDs 1, 2and 3 may be determined in consideration of the production cost and thedesign of the side turn light 16.

[0037] In this light emitting circuit, if the high-luminance LED 5or/and the high-luminance LED 6, both high-luminance LEDs 5, 6 which arethe main light source 16 a to form the first circuit H1, is run down,the voltage applied to the gate (G) of the FET 4 becomes zero.Therefore, an electric current flowing between source (S) drain (D) ofthe FET 4 becomes zero, and the auxiliary light source 16 b to form thesecond circuit H2 also stops the emission of light.

[0038] On the contrary, even if the LEDs 1, 2 and 3 to form the secondcircuit H2 are run down, the first circuit H1 is not affected by theseLEDs, and the main light source 16 a continuously emit light at asufficient luminance to satisfy the regulation.

[0039] As described above, in the side turn light 16 equipped with thelight emitting circuit according to the invention, if the main lightsource 16 a that should satisfy the regulation is run down, theauxiliary light source 16 b also stops the emission of light and theside turn light wholly stops the emission of light. Therefore, the rundown of the main light source 16 a is reliably informed to the driver sothat the driver immediately performs a suitable maintenance.

[0040] Although an LED is employed in the preferred embodiment of theinvention, it is possible to employ a bipolar transistor such that theemitter and the collector of the bipolar transistor are connected in thesecond circuit H2 and the base of the bipolar transistor is connected tothe first circuit H1.

[0041] Also, in the preferred embodiment of the invention, two LEDs areemployed as high-luminance LEDs 5, 6, and three LEDs are employed asLEDs 1, 2 and 3. However, of course, the number of LEDs is not limitedto this specific embodiment.

[0042] Further, in the preferred embodiment of the invention, the lightemitting circuit according to the invention is shown as an exampleapplied to the door mirror 11 (see FIG. 1, etc.). However, the lightemitting circuit may be applied to a fender mirror.

INDUSTRIAL APPLICABILITY

[0043] By the reasons to be described below, a light emitting circuitand a lighting device for a vehicle according to the invention ispreferable for use in a side turn light provided at an outer mirror of avehicle.

[0044] (1) In the light emitting circuit according to the invention,since one end of the first circuit in which is provided a main lightsource is connected to the gate of an enhancement-mode FET (or the baseof a bipolar transistor) and the second circuit in which is provided anauxiliary light source is connected to the source or the drain of thisenhancement-mode FET (or the emitter or the collector of the bipolartransistor), if the main light source is run down, a voltage applied tothe gate (or the base) becomes zero and the auxiliary light source stopsthe emission of light. This makes the driver reliably recognize the rundown of the main light source.

[0045] (2) The lighting device for a vehicle according to the inventionis provided at an outer mirror such as a door mirror and a fendermirror. This lighting device consists of the main light source with asufficient luminous energy that satisfies the regulation and theauxiliary light source that emit light for accessory purposes, and oneend of a first circuit in which is provided the main light source isconnected to the gate of an enhancement-mode FET (or the base of abipolar transistor) and a second circuit in which is provided theauxiliary light source is connected to the source or the drain of thisenhancement-mode FET (or the emitter or the collector of the bipolartransistor). In this construction, if the main light source is run down,a voltage applied to the gate (or the base) becomes zero and theauxiliary light source also stops the emission of light. Accordingly,the run down of the main light source is reliably informed to thedriver.

[0046] (3) In the lighting device for a vehicle and the light emittingcircuit according to the invention, the main light source that requiressufficient luminous energy so as to satisfy the regulation by law isformed by a high-luminance member (e.g., LED), and a low-luminancemember (e.g., LED) with a luminance lower than the main light source isemployed as the auxiliary light source. Therefore, a cheap luminancemember with lower luminance may be used for the auxiliary light source,leading to decreased production cost of the whole lighting device andlight emitting circuit.

[0047] (4) Since the lighting device for a vehicle according to theinvention is incorporated in a door mirror, the side turn light can beprovided at a position higher than the conventional side turn light,leading to improved visibility from others at the time of emission.

1. A light emitting circuit comprising: a first circuit in which isprovided a main light source; and a second circuit connected in parallelwith the first circuit and in which is provided an auxiliary lightsource; wherein a drain and a source of an field effect transistor areconnected in the second circuit, and a gate of the field effecttransistor is connected to the first circuit.
 2. A lighting device for avehicle, which is provided in an outer mirror of a vehicle, comprising:a main light source arranged at a side of the outer mirror; an auxiliarylight source arranged at a front of the outer mirror; and a lightemitting circuit having a first circuit in which is provided the mainlight source, and a second circuit connected in parallel with the firstcircuit and in which is provided the auxiliary light source, wherein adrain and a source of an field effect transistor are connected in thesecond circuit, and a gate of the field effect transistor is connectedto the first circuit.
 3. A light emitting circuit comprising: a firstcircuit in which is provided a main light source; and a second circuitconnected in parallel with the first circuit and in which is provided anauxiliary light source; wherein an emitter and a collector of a bipolartransistor are connected in the second circuit, and a base of thebipolar transistor is connected to the first circuit.
 4. A lightingdevice for a vehicle, which is provided in an outer mirror of a vehicle,comprising: a main light source arranged at a side of the outer mirror;an auxiliary light source arranged at a front of the outer mirror; and alight emitting circuit having a first circuit in which is provided themain light source, and a second circuit connected in parallel with thefirst circuit and in which is provided the auxiliary light source,wherein an emitter and a collector of a bipolar transistor are connectedin the second circuit, and a base of the bipolar transistor is connectedto the first circuit.
 5. A light emitting circuit according to claim 1or claim 3, wherein said main light source emits light at a luminancehigher than said auxiliary light source.
 6. A lighting device for avehicle according to claim 2 or claim 4, wherein said main light sourceemits light at a luminance higher than said auxiliary light source.
 7. Alighting device for a vehicle according to any one of claims 2, 4 and 6,wherein said outer mirror is a door mirror.